This invention relates to packet-based networks such as ATM (Asynchronous Transfer Mode) networks, having a ring architecture. The invention is applicable to both local and wide area networks.
There is a need within networks to ensure that network operation is not interrupted in the event of infrastructure failures, such as cable cuts and/or equipment failure. The current state of the art is to provide protection with SONET Ring architectures. Bellcore standard GR-1230-CORE describes a Bi-direction Line Switched Line Switched Ring and GR-1400-CORE describes a Uni-directional Path Switched Ring.
In the case of ATM networks, the current state of the art is to send ATM payloads over SONET ring structures. As this is an expensive solution, there is a need to provide a simpler mechanism for ATM network protection. While it is possible to map SONET Ring structures directly into an ATM implementation using the ATM Switch to perform the necessary bridging and re-configuration, the result is an inefficient use of the ATM Switch and a slow response time.
An object of the invention is to provide a wide area network architecture that alleviates the afore-mentioned problems of the prior art.
According to the present invention there is provided a communications network a communications network comprising a plurality of nodes interconnected in a ring architecture. A pair of counter-rotating packet-based rings interconnect the nodes to establish virtual connections therebetween. Each node includes a ring interface and a packet switch connected thereto. The ring interface comprises means for extracting packets from either ring destined for the packet switch, means for adding outgoing packets the packet switch to either ring, and means for passing directly through packets on each ring not destined for the node. This results in a virtual mesh structure being established between said nodes.
The rings can either be unidirectional or bi-directional. Of course, it will be understood by one skilled in the art that additional rings can be provided without detracting from the advantages offered by the invention.
The described ring structure allows bandwidth to be efficiently shared between the nodes on the ring without the wastage inherent in a hard-wired mesh and without using up valuable ATM switch resources since onward cells are passed directly through the interface without being forwarded to the ATM switch.
The invention also provides a method of establishing communication over a network wherein a plurality of nodes are interconnected in a ring architecture. A pair of counter-rotating packet-based rings are established to interconnect the nodes and provide virtual connections therebetween. At each node packets destined for the node are extracted from the rings, outgoing packets from the node are added to the rings, and packets on each ring not destined for that node are passed directly through. This results a virtual mesh structure being established between the nodes.